One Spider in Five Hundred and Eighty-One: Diagnosing an Animal That Is Not There

1. Introduction: a title that is a finding

Most papers make you read them. This one does not.

1.1 What this article argues

That the case is a clean worked example of a problem this journal returns to constantly: the difference between a conclusion and the evidence for it, and what happens to a diagnosis when nobody requires the evidence. Sections 9 and 12 are the case.

1.2 And why it matters here

Because a pest control contractor is shown wounds and asked to confirm them, and §20 is about what we can honestly say.

2. The submission study

The measurement, which is as direct as measurements get.

In a nationwide study where people submitted spiders that they thought were brown recluses, of 581 from California only one was a brown recluse, compared to specimens submitted from Missouri, Kansas, and Oklahoma, where between 75% and 90% were recluses.⁴

2.1 The method is the important part

The public was asked to send in the animal rather than to report a sighting. A specimen can be examined by a specialist and a belief cannot.

2.2 And it is a large sample

Five hundred and eighty-one from a single state is not a handful of anecdotes. It is enough that a population present at even a low density should have produced more than one specimen.⁴

That inference is ours and it is the reason the result is persuasive rather than merely suggestive.

2.3 Which controls for the obvious objection

That people in California are simply less familiar with the spider. They may well be, and the method does not depend on their accuracy. It depends on whether the animal arrives in the envelope.

3. What the contrast establishes

Because a low rate on its own would prove nothing.

If submissions everywhere had been mostly wrong, the study would have measured public identification skill. Instead the same request, answered by the same kind of person with the same level of training, returned three quarters to nine tenths correct in the core range.⁴

3.1 This is a control group

Which is rare in the kinds of evidence this journal usually examines. Most claims about pest presence come from one place with nothing to compare against, so a low count means either absence or poor searching and there is no way to tell which.

Here the same protocol ran in two regions simultaneously, and the core-range result is the positive control that makes the California result interpretable.

3.2 So the instrument works

People who live where the spider lives send the spider. People who live where it does not send something else.

3.3 Which is the whole argument in one comparison

The difference between the two figures is not a difference in the observers. It is a difference in what is there to observe, and that reading is ours.

4. The one that counted

The single positive, which is worth its own section.

It was submitted by a family that moved from Missouri and brought it with them.⁴

4.1 A provenance, not a population

The one confirmed specimen in five hundred and eighty-one had a documented route of arrival from inside the native range.⁴

4.2 It also shows the study was done properly

Somebody asked where the specimen came from rather than simply recording a California detection. Had they not, the published figure would have been one confirmed brown recluse in California and the conclusion would have been the opposite one.⁴

A single unexamined record can reverse a finding, which is our observation and the reason provenance is worth the trouble.

4.3 And this is how a correct positive should be handled

Not counted as evidence of local presence, but traced. Our article on detection probability argued that a positive without a provenance is a weaker result than it looks, and this is the version where somebody did the tracing.

5. And the verified specimen record

The longer-run figure.

There are no populations of the brown recluse in California, and fewer than 20 verified specimens have been collected in the state over several decades by spider experts.¹

5.1 What a verified specimen means

An animal in hand, examined by somebody who knows the diagnostic characters, with a location and a date attached. That is the standard the rest of this article measures every other claim against.¹

5.2 Fewer than twenty, over decades, by specialists

Against a state population in the tens of millions and a diagnosis rate the 2003 paper describes as greatly outnumbering verifications.¹

5.3 Two independent lines agreeing

The public submissions in §2 and the specialist collections here are different methods with different biases, and they return the same answer.⁴¹

Which is the strongest form this kind of evidence takes, and our articles on detection repeatedly complain about having only one method.

5.4 The right comparison is not zero

Nobody claims the animal never appears. The claim is that it does not live there, and a small number of verified strays over several decades is exactly what that looks like.

6. Possible against present

The distinction the case turns on.

Over the last century, spiders have occasionally been intercepted in locations where they have no known established populations, and these spiders may be transported fairly easily.⁴

But the lack of established populations well outside the natural range also indicates that such movement has not led to the colonization of new areas, after decades of opportunities.⁴

6.1 Both halves are true

Transport happens. Colonisation does not. A defender of the diagnosis who says the spider could have arrived in a shipment is correct about the mechanism and wrong about the frequency.⁴

6.2 The decades matter

Transport has been happening for a century, which is a long experiment with a consistent result.⁴ Introductions that were going to establish would have done so by now.

Compare our articles on species arriving and spreading, where the pattern is the opposite: something is detected, then found more widely, then found everywhere. That progression is what colonisation looks like, and this species has not shown it.

6.3 Which is the shape of a lot of bad reasoning

A mechanism that exists is treated as an explanation that applies. Our articles on bite misattribution and on client-reported evidence describe the same move in a domestic setting, and this is the version with decades of data attached.

7. The single building case

The honest complication, which the sources state themselves.

The occurrence of brown recluses in a single building (such as a warehouse) outside of the native range is not considered as successful colonization; such single-building populations can occur (e.g., in several such cases in Florida), but do not spread, and can be easily eradicated.⁴

7.1 So a structural population is possible

Which is precisely the kind of thing a pest control contractor would encounter if it happened, and it would be a real finding.⁴

7.2 And it is established by specimens

Not by lesions. The building cases are known because animals were collected there, which is the same standard §2 applies and the reason those reports are credible.

8. Why the diagnosis is made anyway

The explanation the researchers give, in their own words.

Many people self-diagnose another skin condition as this bite because it's a sexy diagnosis; it's like saying you were bitten by a rattlesnake. It's dramatic. Bacterial infections? Not so much.²

And physicians tend to falsely diagnose it because it's a really comfortable scapegoat. People want a diagnosis. Doctors want to give them a diagnosis, so if physicians can't figure out the identity of an ambiguous bump, they jump to spider bite.²

8.1 A diagnosis of exclusion becoming a diagnosis of convenience

Which is the mechanism, and it does not require anybody to be careless. It requires only that an unexplained lesion is uncomfortable for both parties and that a name is available.

8.2 The structure of a self-confirming belief

A wound is attributed to a spider. The attribution is not tested because no specimen is required. The case joins the informal record of bites in the area. The record makes the next attribution seem more reasonable.⁵

Nothing in that loop touches the animal at any point, which is why it can run indefinitely in a place where the animal is absent. That reading is ours.

8.3 The media contribution

The spider has also received numerous sensationalized media reports of bites occurring where these spiders are absent (and no specimens were found).⁴

9. The missing step

Stated plainly by one source.

The diagnosis is further complicated by the fact that no attempt is made to positively identify the suspected spider.⁵

9.1 And the specimen standard is available

This is not a case where the required evidence is impossible to obtain. A spider in a jar can be identified by a specialist, and the sources note that specialists will do it.⁵

Which distinguishes this from most of the measurement gaps this journal reports. The method exists, is cheap, and is not used.

9.2 That is the whole problem in one sentence

A diagnosis naming a species is being made without the species being examined, in a case where several certified arachnologists are able to positively identify a brown recluse specimen on request.⁵

9.3 And the timing compounds it

A wound found one week later may be misattributed to the spider.⁵

So the patient is often not reporting a bite they witnessed. They are reporting a wound they noticed and an explanation they constructed, which our article on client-reported evidence describes as the ordinary case rather than the exception.

10. What the lesion actually is

The alternatives, which are the point of the whole exercise.

Around 40 conditions have been or could be misdiagnosed as this bite, including Lyme disease, herpes, antibiotic-resistant staph infection, diabetic ulcers.²

The 2017 paper's authors note that infections caused by six named organisms, and even lymphoproliferative conditions, have been misdiagnosed as this bite.⁷

10.1 The list is not reassuring

An infection that resists first-line antibiotics, a disease that becomes chronic if untreated, a fungal infection acquired through a skin injury, and a lymphoproliferative condition.⁷

These are not conditions that resolve while being observed, which is §11.

10.2 Why the confusion is understandable

Skin wounds are common and infections will lead to necrotic wounds, thus many severe skin infections are attributed falsely.⁵

A necrotic lesion is a common endpoint of many processes, and an endpoint does not identify its cause. Which is the same logic our detection articles apply to evidence of a pest: damage is consistent with many things.

11. The cost of the wrong answer

Why this is not a pedantic complaint.

When we see people with cancer or MRSA who get this false diagnosis, it really drives home that you can't just call everything a recluse bite.²

11.1 The failure mode is delay

A lesion attributed to a spider is a lesion that is being observed rather than treated, and two of the alternatives in §10 are an aggressive infection and a malignancy.⁷²

11.2 One researcher's framing

I'm really on a crusade here. We have this knowledge that is counter to what many doctors and the general public are saying. And what they are saying is causing damage by misdiagnosis.³

12. The rule-out instrument

The response the researchers built.

A 2017 dermatology paper by two dermatologists and an entomologist introduces a mnemonic device to describe the most common skin signs that are misdiagnosed as brown recluse bite.³⁶

12.1 The publication venue matters

A dermatology journal rather than an entomology one.⁶ The people making the error are clinicians, and a correction published where entomologists read it would reach the wrong audience.

Which sounds obvious and is not always done. Our journal has noted several times that findings about pest biology sit in literatures the practitioners never open.

12.2 Note the authorship

Two clinicians who treat these bites and an entomologist who identifies the spiders.⁶⁷ Which is the combination the problem requires, and this journal's usual complaint is that it does not happen.

13. The ten items

The instrument itself.

The items are given as Numerous (should be solitary), Occurrence (wrong geography), Timing (wrong season), Red Center (center should be black), Elevated (should be shallow depression), Chronic, Large (more than 10 cm), Ulcerates too quickly (less than a week), Swollen, Exudative (there should be no pus, it should be dry).⁵

13.1 Each item is a contradiction

Not a symptom of the bite but a sign inconsistent with it. The instrument is a list of things that should be absent.⁵

13.2 And the authors supply alternatives

They also offer alternate diagnoses that are more likely for many of the acronym categories.⁸

Which is what makes it usable. A tool that only says no leaves the clinician where they started, and the reason the wrong diagnosis was reached in §8 is that no better one was available.

14. Why two

The threshold.

Tally two or more signs and the diagnosis should be reconsidered.²

14.1 A threshold is a policy choice

Any exclusion rule trades two errors against each other: discarding correct diagnoses and retaining incorrect ones. Where the threshold sits states which error the designers were more worried about.

Two out of ten is low, which says they were more worried about the false positive, and §11 explains why that is the right worry here.

14.2 Not one

Which is a deliberately forgiving threshold. A single unusual feature could be individual variation, an unusual presentation or an error of observation, and requiring two protects against discarding a correct diagnosis on a single discrepancy.

14.3 And not five

A high threshold would preserve the problem the tool exists to solve. Two of ten is a low bar to clear and that is the design intent, which is our reading.

15. What a real bite looks like

The positive description, for completeness.

Bites are whitish blue or purple (not red), flat (not elevated) and don't last more than 3 months.³ A typical bite is a single focal lesion, and bites do not express pus and are nonexudative.⁸

15.1 The bite is real and serious

One source describes it as rapidly causing an infarction in skin that is painful and can be slow to heal, and states that this is the only North American spider to cause such severe necrosis, sometimes producing a sudden, severe hemolysis.⁸

Deaths have been reported in children.¹

15.2 Note how specific the positive description is

Colour, elevation, number, exudate and duration are all specified, and each is falsifiable.³⁸

Which is what makes the exclusion tool possible. A condition described only in vague terms could not generate a list of contradictions.

15.3 So this is not a debunking

Within the range, the animal and the injury are both genuine. The argument concerns where the diagnosis is applied, not whether the condition exists, and we want that clear.

15.4 And the treatment finding is worth recording

One review concludes that conservative care without drugs is the safest proven treatment.⁸

16. The design choice worth admiring

Why the instrument is built the way it is.

Confirmation is unavailable. Nothing about a wound identifies the animal that made it, and §9 establishes that the animal is usually not examined.⁵

16.1 Which is not the usual clinical instinct

Diagnostic tools are normally built to identify. An instrument whose output is only ever that something is not the thing in question is asking the clinician to accept an unresolved case, at least until the alternatives are worked through.

That is a harder thing to publish than a confirmatory checklist, and §8 explains why it was necessary: the whole problem is that an unresolved case was intolerable.

16.2 But exclusion is available

Because the real injury has known properties, anything lacking them is something else.³

16.3 Which is the correct response to an unidentifiable cause

This journal has repeatedly wanted a confirmatory test and not found one. The lesson here is that where confirmation is impossible, a well-built exclusion is not a consolation prize. It is the appropriate instrument, and it is more honest than a confirmatory test with a poor specificity would be.

That is our conclusion and we intend to apply it elsewhere.

17. Geography is one item of ten

A detail in the instrument's design that we did not expect.

Occurrence, meaning wrong geography, is one criterion among ten.⁵ It is not decisive on its own.

17.1 The authors could have made it decisive

Given §§2 to 5, a rule saying no populations here means no bites here would be defensible and simpler.

17.2 Why we think they did not

Because §§6 and 7 are true. Individuals are transported and single-building populations occur, so a categorical geographic exclusion would occasionally be wrong, and a tool that is occasionally and confidently wrong is harder to trust than one that weights.

That is our reading of the design and not something the authors state.

17.3 One source describes the item differently

As meaning the wound did not occur in a place where Brown Recluses are likely to be found,⁷ which reads as the immediate setting rather than the region, and our sources do not resolve which is meant.

18. The Canadian sentence

The line that puts this article in this journal.

These false diagnoses occur all over North America, even in American states and Canadian provinces where no brown recluse populations are known to exist.⁷

18.1 Which is not a throwaway

The paper's authors are American, writing for an American clinical audience, and they went out of their way to include another country's jurisdictions in the statement of where the false diagnoses occur.⁷

18.2 Canadian provinces, stated by the authors

Not inferred by us.⁷

A second source lists regions of North America where the diagnosis is reinforced despite the spider not being endemic.⁵

19. Which makes this a Manitoba article

The local application, which is unusually direct.

The species is native to the southern and central midwestern United States, and this province is not in that range by any account we read.

19.1 So the geography criterion is satisfied here by default

Every suspected recluse bite in Winnipeg carries at least one of the ten items before anybody looks at the wound.⁵

19.2 Which is one, and two are needed

So the instrument does not settle the question by itself, and that is §17 applied locally.

19.3 And the species that are here

A client who has a spider, and can produce it, almost certainly has one of the species that actually live in this province, none of which is a recluse. Our article on spider identification accuracy covers what the common ones are and how often they are mistaken.

Which means the useful conversation is about the animal in the jar rather than about a species from a thousand kilometres away.

19.4 What we could not find

Any Canadian or Manitoba figure for how often this diagnosis is given, any provincial verified specimen record, and any published survey of which spider species are actually present in Winnipeg buildings.

20. What a contractor is actually asked

The situation, as it arrives.

A client has a wound. They have often already been told, or have concluded, that a spider caused it. They want a pest control contractor to confirm it and to treat the house.

20.1 Two requests, and they are different

Identify an animal, which we can attempt if there is an animal. And explain a lesion, which we cannot do at all.

20.2 And there is a third request underneath

Reassurance. A person with an unexplained wound and a frightening name attached to it wants to be told they are not in danger, and neither of the two requests in §20.1 delivers that.

Which is why the conversation is harder than it looks, and why §21.1 treats the tone as part of the answer rather than as decoration.

20.3 The second is the one being asked

Usually without the first being possible, because there is no specimen.⁵

21. And what we should say

Our position, stated so it can be held to.

We identify specimens. Bring the animal, in a container, and we will try, and if it matters we will say when we are not certain.

We do not diagnose wounds. No pest control licence qualifies anybody to do that, and our articles on scope and on certification describe what the licence actually covers.

The geography is worth stating. The species has no populations in this province, which is a fact and not a diagnosis.⁷

And the referral is the service. A doctor about the wound, and us about the building if there is an actual arthropod problem.

21.1 The tone matters as much as the content

A client who has arrived with a frightening belief and is told flatly that they are wrong will go somewhere that agrees with them. Our article on the psychological burden of infestation describes why the fear is not irrational even when the identification is.

So the honest version is not a correction. It is that the wound needs somebody qualified to look at it, which is a stronger reason to see a doctor than the client arrived with.

22. Why agreeing is not harmless

The part that makes this a matter of conduct rather than accuracy.

A contractor who nods along has given an authoritative-sounding confirmation of a diagnosis that may be delaying treatment for a resistant infection or a malignancy.²⁷

22.1 And it is commercially convenient to agree

Which is the uncomfortable part. A confirmed spider problem is a treatment sale and an unexplained wound is not.

Our credence goods article established that the client cannot check our claims. This is the case where an unverifiable claim in our favour could cost them something that matters far more than the fee.

22.2 And the inspection still has value

Declining to confirm the diagnosis does not mean declining the visit. A building can be inspected, the spiders present can be identified, and the harbourage conditions can be described.

What comes back is a factual account of what lives in the building, which is a real answer to a question adjacent to the one asked, and is more than the client had.

22.3 So the rule is simple

We do not confirm a bite we did not see from an animal we were not shown.

23. What this shares with the rest of this journal

The connections.

The specimen standard. Our articles on identification accuracy and on molecular diagnostics both argue that a name requires evidence, and this is the case where the absence of that requirement is quantified.⁴

The uninterpretable positive. Our environmental DNA article warned that a detection in a commercial context creates liability, and §4 shows what a properly traced positive looks like.

The dramatic explanation displacing the likely one. Our bite misattribution article, with this as the version that has a named species and a published literature.²

And the mechanism treated as the explanation. Section 6.3.

23.1 But one thing is different here

This journal normally ends by reporting that the measurement nobody made would settle the question. In this case somebody made it, twice, by two methods, and published the result.⁴¹

The diagnosis continues anyway, which is a more discouraging finding than a missing measurement and a more useful one. It shows that data is not by itself sufficient, and that a replacement for the answer being removed has to be supplied, which is what the alternate diagnoses in §13.2 are for.

24. Our own position

The disclosure.

We sell spider treatments. A client convinced they have a dangerous spider is a client who buys one, and §22.1 says why we should be suspicious of our own agreement in that conversation.

24.1 What we do sell honestly

Spider management in a building is a real service for a real problem, which is web accumulation, nuisance numbers and the insects the spiders are eating. Our articles on exclusion and on prey availability describe the work.

None of it requires the client to have been bitten by anything.

25. Limitations and open questions

The 2003 study is cited by title. We have the finding from the title and the citation in a university reference page, not from the paper itself.¹

The 581 figure reaches us through a tertiary source. A general reference compilation citing the original, flagged accordingly.⁴

The mnemonic's expansion likewise. The ten items in §13 come from a general reference compilation rather than from the paper, which we could not access.⁵

The forty conditions figure is journalistic. Reported in a news article rather than sourced to a count in the paper.²

The sources disagree on one item. Section 17.3.

And everything is American. The range, the diagnosis rates, the specimen records and the clinical material. The Canadian statement is one clause in one source.⁷

Sections 1.1, 2.1, 3.2, 4.2, 5.2, 6.2, 7.2, 8.1, 9.2, 10.1, 13.2, 14, 16.2, 17.2, 19, 20, 21, 22, 23 and 24 are our reasoning. The reading of the submission study's design, the possible against present distinction, the interpretation of the exclusion instrument and its threshold, the account of why geography is weighted rather than decisive, and the whole of the contractor conduct argument are ours rather than sourced positions.

26. Conclusion

Five hundred and eighty-one people in California collected a spider they believed was a brown recluse and sent it to be examined. One was. That one had been carried from Missouri by a family that moved. The same request in Missouri, Kansas and Oklahoma returned between three quarters and nine tenths correct, so the instrument works and the difference is in what is there to find.⁴ Fewer than twenty verified specimens have been collected in the state across several decades by specialists, and the paper that opened this subject has the finding in its title: diagnoses greatly outnumber verifications.¹

The reason is stated without much charity by the people who studied it. It is a dramatic diagnosis, it is a comfortable scapegoat, people want an answer and doctors want to give one, and when an ambiguous lesion has no obvious cause the spider is available. Around forty conditions have been mistaken for it, among them a resistant staphylococcal infection, anthrax, Lyme disease, a soil fungus, shingles and a lymphoproliferative skin condition, and the harm is that a wound attributed to a spider is a wound being watched rather than treated.²⁷

What the researchers built in response is worth more than the debunking. Confirmation from a lesion is impossible, so they wrote down ten things a real bite is not, and set the threshold at two. That is the right instrument for a question that cannot be answered positively, and it is more honest than a confirmatory test with poor specificity. Wrong geography is one item of the ten rather than a rule of its own, which we read as the authors declining to be categorically wrong in the rare case. The authors note these false diagnoses occur in Canadian provinces where no populations are known to exist,⁷ which is this province, and means that a client here arrives with one of the ten items already satisfied and nine still to check by somebody qualified to check them. That is not us.

References

1. Brown recluse and other recluse spiders, university statewide integrated pest management program pest note, authored by a specialist in this subject. Used for the statement that many skin lesions are misdiagnosed as brown recluse bites with potentially debilitating and potentially fatal consequences; for the position that contrary to popular belief there are no populations of the named species in California and that fewer than twenty verified specimens have been collected in the state over several decades by spider experts, despite people frequently relating accounts of bites or receiving such a diagnosis from a physician; for the note that four species of native recluse spiders occur in southern areas of that state and can cause similar effects; for the report that deaths have been reported in children; and for the bibliographic citation of a 2003 toxicology journal paper whose title states that diagnoses of brown recluse spider bites greatly outnumber actual verifications of the spider in four western American states. https://ipm.ucanr.edu/home-and-landscape/brown-recluse-and-other-recluse-spiders/
2. Brown recluse spider bites are often misdiagnosed, national broadcaster health news article. Journalistic source reporting on a published paper, cited as attributed material. Used for the account that the mnemonic stands for features that would not be present if a patient had been bitten, with a tally of two or more indicating reconsideration; for the quoted explanation from a retired university entomologist that people self-diagnose because it is a dramatic diagnosis, compared to being bitten by a rattlesnake, whereas bacterial infections are not; for the observation that such self-diagnoses occur outside the species range; for the quoted explanation that physicians falsely diagnose it because it is a comfortable scapegoat, that people want a diagnosis and doctors want to give one, so an ambiguous lesion is attributed to a spider bite; for the quoted remark that seeing people with cancer or a resistant staphylococcal infection receive this false diagnosis demonstrates that not everything can be called a recluse bite; for the statement that around forty conditions have been or could be misdiagnosed as this bite, including a named tick-borne disease, a named viral infection, antibiotic-resistant staphylococcal infection and diabetic ulcers; and for the note that the spiders are reclusive so bites are more apt to happen in places such as closets or attics. https://www.npr.org/sections/health-shots/2017/02/16/515576450/is-that-a-brown-recluse-spider-bite-or-skin-cancer
3. No, that's not a brown recluse spider bite, university entomology department news release. Used for the account that the entomologist and two dermatologists from a named university health sciences centre introduced the mnemonic in a dermatology journal to describe the most common skin signs that are misdiagnosed as this bite; for the worked example that three letters of the mnemonic indicate red, elevated and chronic, whereas real bites are whitish blue or purple rather than red, flat rather than elevated, and do not last more than three months, so that a wound which is elevated, red or persists beyond three months should prompt consideration of something else; and for the quoted statement that the researcher regards this as a crusade, that the knowledge runs counter to what many doctors and the general public say, and that what they are saying is causing damage by misdiagnosis. https://entomology.ucr.edu/news/2017/02/15/no-thats-not-brown-recluse-spider-bite
4. Brown recluse spider, general reference compilation entry. Tertiary source citing primary literature, flagged accordingly. Used for the report of a nationwide study in which people submitted spiders they believed were brown recluses, of which 581 came from California and one was a brown recluse, submitted by a family that had moved from Missouri and brought it with them, compared with submissions from Missouri, Kansas and Oklahoma where between 75 and 90 per cent were recluses; for the note that other species of the same genus native to the south-western United States may resemble the brown recluse but that interactions with humans are rare because those species' native ranges lie outside dense human populations; for the statement that over the last century spiders have occasionally been intercepted in locations with no known established populations and may be transported fairly easily, but that the lack of established populations well outside the natural range indicates such movement has not led to colonisation after decades of opportunities; for the position that occurrence in a single building such as a warehouse outside the native range is not considered successful colonisation, that such single-building populations can occur but do not spread and can be easily eradicated; and for the note that the spider has received numerous sensationalised media reports of bites occurring where the spiders are absent and no specimens were found. https://en.wikipedia.org/wiki/Brown_recluse_spider
5. Loxoscelism, general reference compilation entry. Tertiary source citing primary literature, flagged accordingly. Used for the statements that many necrotic lesions are erroneously attributed to this bite, that skin wounds are common and infections lead to necrotic wounds so many severe skin infections are falsely attributed, and that many suspected bites occurred in areas outside the species' natural habitat; for the note that a wound found one week later may be misattributed to the spider; for the statement that the diagnosis is further complicated because no attempt is made to positively identify the suspected spider, so other non-necrotic species are often misidentified, and that several certified arachnologists can positively identify a specimen on request; for the observation that reports reinforce improbable diagnoses in regions of North America where the spider is not endemic, naming three; and for the expansion of the ten-item mnemonic as numerous rather than solitary, occurrence meaning wrong geography, timing meaning wrong season, red centre where the centre should be black, elevated where there should be a shallow depression, chronic, large meaning more than ten centimetres, ulcerating too quickly meaning within a week, swollen, and exudative where there should be no pus and the lesion should be dry. https://en.wikipedia.org/wiki/Loxoscelism
6. Bibliographic record for the mnemonic paper in a dermatology journal, national library of medicine database. Used for the publication details, namely the paper title, the journal, the 2017 publication date, the volume, issue and page numbers, the digital object identifier, and the three authors with their affiliations at a named company and the dermatology and entomology departments of two named universities. https://pubmed.ncbi.nlm.nih.gov/28199453/
7. New mnemonic to prevent misdiagnosis of skin conditions as spider bites, dermatology news site article. Secondary reporting on the published paper, cited as attributed material. Used for the account that the paper's authors note infections caused by six named organisms, spanning bacterial, tick-borne, fungal and viral causes, and even lymphoproliferative conditions, have been misdiagnosed as bites from this spider; for the statement that these false diagnoses occur all over North America, even in American states and Canadian provinces where no brown recluse populations are known to exist; for the description of the mnemonic as describing the most common skin signs that are not associated with the bite but occur in misdiagnosed lesions; and for the gloss of the occurrence criterion as meaning the wound did not occur in a place where these spiders are likely to be found. https://www.derm.city/post/2017/02/22/not-recluse-new-mnemonic-to-prevent-misdiagnosis-of-skin-conditions-as-spider-bites
8. Research repository record for the mnemonic paper, reproducing the abstract and related material. Repository listing rather than the primary paper, flagged accordingly. Used for the expansion of the mnemonic's ten terms; for the statements that real bites do not express pus and are nonexudative, that a typical bite is a single focal lesion, and that such bites are flat or slightly sunken; for the description from a cited work that the bite rapidly causes an infarction in skin that is painful and can be slow to heal, that this is the only North American spider to cause such severe necrosis, that the bite can sometimes produce a sudden severe haemolysis, and that conservative care without drugs is the safest proven treatment; for the reference to a retrospective review of nineteen documented cases in a university dermatology clinic over a stated period, with the sex and age range of patients and the supportive measures used; and for the note that the authors offer alternate diagnoses that are more likely for many of the mnemonic's categories. https://www.researchgate.net/publication/313783310_NOT_RECLUSE-A_Mnemonic_Device_to_Avoid_False_Diagnoses_of_Brown_Recluse_Spider_Bites